Compiled by Jana Škorpilová, Petr Voříšek, Arco Van Strien, Willy Van Strien, Ian Burfield and Richard D. Gregory
Bird monitoring in Europe is organized on a national level; most countries have developed their monitoring schemes rather independently. National monitoring schemes are organized mostly by NGOs with various involvements of other institutions and individuals (governmental agencies, universities, research institutes etc).
The national bird monitoring schemes employ an array of different methods that are approved by PECBMS. The national coordinators provide PECBMS with the results of their schemes according to agreed standards and formats. Each national scheme delivers indices of numbers of individual bird species and trends therein as its main output; the index is the time series of the numbers, the trend is the change in these numbers over the years. These national indices and trends are the source of data for PECBMS, which uses them to compute supranational species indices and trends and multispecies indicators.
For details and contacts to national schemes´ coordinators visit Common bird monitoring schemes in Europe
1.1 Counting birds
Birds are counted using standardised field methods (for details see Box Field methods). Since complete counts are nearly impossible for large spatial units, birds are counted at sample plots selected across a territory of a country (for details see Box Selection of sample plots). Although field methods, selection of sample plots, and also number of years covered differ among European countries, statistical methods can handle this (see chapter 2.2. Combining national data into supranational outputs). Birds are counted within national generic breeding bird monitoring schemes, where all species registered are counted. However, some species are not covered well by these schemes, such as species with nocturnal activity (e.g. owls) or cryptic life style, some clustered and colonial species or extremely rare species. For such species or groups of species, specific surveys need to be set up, but these are not the focus of PECBMS.
Survey results can be affected by the fact that only part of the birds present at a particular site at the moment of counting is detected by an observer. This ´detection probability´ is variable over space and time and may also differ between observers. This should be addressed in field methods and data analysis. New methods are currently being developed to do so.
The majority of field work (i.e. bird counts) is done by volunteers and managed by coordinators. Since bird watching is a widespread activity across Europe and elsewhere, it is often no problem to recruit a high number of volunteers for bird surveys, and this is relatively easy in comparison to other taxa. Just as professionals, volunteers must be able to identify the birds in the field properly, record field data accurately and in proper format and deliver them timely to the coordinators. Since the volunteers do their work for free, one might fear that their work suffers from this, but such fear is unnecessary. Coordinators use a wide array of methods to check the skills of the volunteers and to guarantee a high standard of the data delivered.
One possible problem connected to working with volunteers is the selection of sampling plots. Volunteers might prefer to count in areas that are rich in birds rather than to be directed to plots which have been selected randomly. To solve this problem several national monitoring schemes select sample plots in a stratified random manner. Another problem is that volunteer fieldworkers can leave a scheme at any moment, causing a turnover in the sites counted and missing values. This occurs in any long-term monitoring scheme and statistical techniques and software are widely available and used to solve this problem too.
While the potential risks linked to the involvement of volunteer fieldworkers have been solved, several advantages remain: the running costs of a scheme are relatively low and large-scale schemes are feasible (Greenwood, 2007).
For more details on each national monitoring scheme visit Common bird monitoring schemes in Europe.
1.2 Production of national indices and trends
Population yearly indices and trends are the most important outputs of national monitoring schemes. The index gives bird numbers in percentages relative to a base year, when the index value is set at 100%. Usually, but not necessary, the first year of a time series is chosen as the base year. Trend values express the overall population change over a period of years.
National species indices are produced by the coordinators of the monitoring schemes. They assess yearly all-sites totals per species and compute the individual national species indices in a prescribed way. The count data usually contain missing values, and to impute these they use the predominant statistical technique, that is, Poisson regression, as implemented in the TRIM software (Trends and Indices for Monitoring data, Pannekoek & Van Strien, 2001). TRIM is a widely used freeware program (available via http://ebcc.birdlife.cz). To facilitate the use of TRIM, the software tool BirdSTATs is available too.
Statistically spoken: the basic TRIM model contains both site effects and year effects and estimates missing values from the data of all surveyed sites:
with αi the effect for site i and γj the effect for year j on the natural log of expected counts μij. Missing counts for particular sites are estimated (´imputed´) from changes in all other sites, or in sites with the same characteristics if the basic model is extended with covariates. The assumption is that changes observed in surveyed sites also apply to non-surveyed sites.
The program produces imputed yearly indices and totals for each species. These yearly scheme totals, together with their standard errors and covariances, are collected by the PECBMS coordinator.
For details on TRIM and BirdSTATs, see Box Missing values I.
In case there is more than one monitoring scheme within a country, e.g. an old scheme and a new one (i.e. schemes differ in time span) or different regional schemes (i.e. schemes differ in spatial coverage), the coordinator combines the results per scheme to produce new combined indices per species and per country. A tailor-made software tool called Combine has been developed for this purpose, which also takes into account standard errors of indices of the constituent schemes. The procedure used resembles the one to produce supranational indices from national results (see below).
In addition to national indices, trends are computed to indicate whether long term changes in bird populations are strongly increasing, moderately increasing, stable, uncertain, moderately declining or steep declining (learn more in Box Trend interpretation and classification).
2.1. Delivery of national data to PECBMS coordination unit
Box Data checks
Box Participating countries
2.2. Combining national data into supranational outputs
Box Missing values II
2.3. Types of supranational results that PECBMS produces
2.1. Delivery of national data to PECBMS coordination unit
Coordinators of national monitoring schemes deliver their national data to the PECBMS coordination unit annually. For information on data and contributing countries see Box Participating countries.
The data delivered are: the national yearly indices per species, the all-sites yearly totals (= the sum of birds counted across all sites per year) and their standard errors, and the covariances between the yearly figures.
Specifically, national coordinators deliver two files per species – so called out and ocv files (see paper by Pannekoek & Van Strien, 2001 or also see website of Statistics Netherlands) – both produced by TRIM when calculating species indices at the national level. These TRIM output files are accompanied by a species list and by comments indicating any potential problems in the data. These comments are taken into account in further data analysis.
National data are checked for their quality using quantitative criteria (see Box Data checks).
2.2. Combining national data into supranational
A method has been developed to produce supranational yearly totals and their standard errors across countries by combining the national data. The method takes into account the differences in population sizes per country, as well as the differences in field methods and in the numbers of sites and years covered by the national schemes. Instead of deriving the standard errors in the usual statistical way from count data and model fit, standard errors (and the year-year covariances) that resulted from the calculation of the all-sites totals per country were applied. The results are similar to those that would be produced when the raw data are being used (Van Strien et al, 2001).
To produce supranational indices, the national all-sites totals per species as assessed in the national monitoring schemes are combined. A weighting factor is introduced to adjust for differences in national population sizes, to make sure that a change in a larger national population has an accordingly greater impact on the overall trend than a change in a smaller population. The weighting factor is calculated as the national population size derived from BirdLife International (2015) in 2008-2012 divided by the average of the all-sites totals for 2009-2011. This weighting factor is applied to all other years of the scheme. By this weighting, the yearly scheme totals are converted into yearly national population sizes.
The national European monitoring schemes have started in different years, leading to missing national all-sites totals. An adapted version of TRIM is used to estimate the missing country totals, in a way equivalent to imputing missing counts for particular sites within a country. After these weightings and imputation steps, the national totals are summed up to European totals.
European species indices for a species are computed if data are available from countries which together host at least 50% of the ´PECBMS European´ population of that species. ´PECBMS Europe´ is EU 27 + Norway and Switzerland and consists of those countries which already deliver their data to PECBMS or are supposed to do so in the near future: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Norway, Poland, Portugal, Republic of Ireland, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, United Kingdom.
However, some parts of these countries (states) were excluded, mainly because of their far distance to the mainland of Europe: Faroe Islands and Greenland, Svalbard, Azores, Madeira, Canary Islands, Gibraltar.
Population species trends (multiplicative slopes) are computed and classified in the same way as at the national level.
2.3. Types of supranational results that PECBMS produces
Species indices and trends are produced for Europe and its regions (Central & East, North, South, West, and Southeast Europe, East Mediterranean and West Balkan) and for EU and its regions: New (since 2004) and Old EU Members States).
The species indices are always computed for maximum time period given by the country with the longest data set within the region (e.g. indices for West Europe are produced since 1966 given by the starting year of the indices from UK, while indices from South Europe are produced since 1989 given by the starting year of indices from France – see an overview below).
Overview showing list of 28 countries, their start years and region that each country belongs to:
|Country/region||Region(group of countries)||First year||Last year|
|Republic of Ireland||WE||1998||2016|
WE – West Europe
NE – North Europe
SE – South Europe
SEE – Southeast Europe
CEE – Central & East Europe
First year – first year of data time series in a country/region
Last year – last year of data time series in a country/region
Time series for individual species from national schemes are shorter in certain cases.
1) Data for Belgium were combined from Wallonia and Brussels regions.
2) Data for Cyprus come from two schemes that partly differ in their regional coverage, Volunteer Common Birds Census (2006-2016) and Western Cyprus Common Bird Census (2006-2011). Data from both schemes were combined.
3) Data for France come from two schemes, old (1989-2001) and new one (2001-2016). Data from both schemes were combined but not updated this year.
4) Data for Germany were combined from schemes in former East and West Germany and also newly from old scheme (Häufige Brutvögel alt, 1989-2010) and new scheme (Häufige Brutvögel neu, 2005-2016).
5) Data for Latvia come from three different schemes, two old ones (differ in their regional coverage, and cover the periods 1995-2006 and 2003-2006, respectively) and a new one (2005-2016). Data from all schemes were combined.
6) Data for Norway come from three schemes, Norsk Hekkefugltaksering, HFT (1996-2008), Terrestrisk overvåking, TOV-I (1996-2008) and Terrestrisk overvåking – Ekstensiv, TOV-E (2006-2016). Data from all schemes were combined.
7) Data for Sweden come from two schemes, old (1975-2015) and new one (1998-2016). Data from both schemes were combined.
Although we produce all species indices for the maximum time period (since the first year of time period available), we publish only the European indices since the year 1980 at the earliest since when the index is based on data from several countries – see the latest version of species indices and trends.
The species trends are produced for the maximum time period and for shorter periods as well: since 1980, 1990, 2000, 2007 and 2012. For simplicity only, we publish the long-term trends (the trends which starting year varies from 1980 to 1998) and the ten-year trends (the trends for last ten years, i.e. 2007-2016).
Supranational species indices are combined in multispecies indicators. These are produced for groups of species according to their main habitat types. To produce precise indicators with small standard errors, it is important to include as many bird species as possible. The rationale behind the construction of composite indicators is that each species is seen as a replicate that may respond in the same way to environmental drivers as the other species and repeats the same signal.
After the supranational species indices have been produced, species are checked for their suitability to be included in the indicators. If a species trend (i.e. multiplicative trend) is classified as ´uncertain´ AND if the index value is > 200 % or < 5 %, data are considered doubtful and the species index and data quality are examined in detail. The decision to exclude such a species from an indicator depends on whether this species was already used in previous versions of the indicators, whether better data can be expected in the near future and whether index fluctuation is believed to be caused either by poor data or by other reasons linked to methodology.
To produce multispecies indicators, we used an indicator tool (MSI-tool) developed in Statistics Netherlands. The tool produces the same outputs as in the previous updates of the indicators and also the smoothed values with confidence intervals and trend of the indicator. For more details on the tool and statistical procedure please check Soldaat et al. (2017).
For some species the available time series started later than first year. In such cases, the multispecies index has been calculated using the chaining method (e.g. Marchant et al., 1990; Ter Braak et al., 1994) that is incorporated in the indicator tool, assuming that the average change in all other species of the indicator reflects the changes of the focal species during the period that is missing.
As with species trends and indices, the interannual consistency of the indicators is examined: new versions are compared with previous ones. In case any inconsistency is found, we investigate whether this is caused by improvements in the data (e.g. improved national data sets, longer time series, new countries contributing their data) or by a computation error.
Indicators are produced for common farmland birds, common forest birds and all common birds. We developed the PECBMS European species classification to classify the bird species.
The indicators are produced for Europe, EU, but also for four European regions (Central & East Europe, North Europe, South Europe, West Europe) and for two EU regions (Old and New EU).
The regional indicators are produced in two versions: one according to the PECBMS European species classification and one according to the regional classification system, which may differ a little.
For list and graphs of the indicators produced, see the latest update of European indicators.
The European Bird Census Council are encouraging registration for their 21st Conference “Bird Numbers 2019”, to be hosted by the LabOr – Laboratory of Ornithology in the beautiful Portuguese city of Evora, 8-13th April 2019.
Bird Numbers 2019 will cover a broad range of topics related to the monitoring of birds and their ecology and conservation, at both national and continental scales, and will consider the wider relevance of such work for science, conservation and society. The conference will feature invited plenary speakers, parallel lecture sessions, posters, thematic workshops, excursions and cultural events.
Whilst the exciting programme of plenaries, lecture sessions and workshops is now finalised, the deadline for the submission of poster abstracts is 31st January.
Suitable subject areas include:
– atlases and studies of bird distributions;
– biodiversity indicators;
– surveys and monitoring of breeding birds;
– waterbird monitoring;
– new methods and technologies;
– changes in wintering areas: long-distance migrants and migratory connectivity;
– causes of change in bird populations and societal responses;
– climate change impacts;
– renewable energies and their effects on birds;
– effects of conservation actions and policies.
Bird numbers 2019 is a collaboration between the EBCC, LabOr, the Institute of Mediterranean Agricultural and Environmental Sciences (ICAAM) and the University of Evora. We look forward to seeing you in Portugal for what will undoubtedly be a memorable conference.
The first Atlas of Wintering and Migratory Birds of Portugal is the largest collective ornithological work of the last 10 years in the country and is finally published. Field work produced almost 4000 hours of census and 150 thousand bird records, covering three quarters of the national territory in systematic visits. In all, more than 400 bird species have been registered. These are extraordinary results for a project of national scope, whose field work was carried out in only two years.
The project was co-funded by the EDP Biodiversity Fund 2010 and involved the following entities: SPEA (Portuguese BirdLife Partner), LabOr – Laboratory of Ornithology, ICAAM, University of Évora, ICNF, Institute of Nature and Forestry Conservation, Institute of Forestry and Nature Conservation, Regional Secretariat for Energy, Environment and Tourism (Azores), and the Portuguese Association of Bird Ringers.
The Atlas is published in Portuguese and is available only online at http://bit.ly/atlas_aves
Since the 19th of September 2018 you can visit the brand new website of the PanEuropean Common Bird Monitoring Scheme here:
The new presentation of the graphs enables to perform the data for several selected species or indicators in one graph to facilitate the comparison. If you wish to check, how are, for example, the European species of tits doing, just order the table by taxonomy, tick all the tits, choose “All data in one graph” and click on “Show” button. You will see all the six species trends in one graph. Guess, which tit species is doing the best and the worst?
We tried to make the website user-friendly, comprehensive and up to date.
However, we are aware that the website needs to be improved continuously.
Please, if you have some comments or questions, do not hesitate to let us know!
Since last autumn we spread a quarterly newsletter which aims to bring the news regarding all EBCC projects – Pan-European Common Bird Monitoring (PECBMS), European Breeding Bird Atlas 2 (EBBA2) and EuroBird Portal (EBP) – to everybody who is interested in bird monitoring in Europe. We wish to stay in touch and communicate together.
Are you the national coordinator of monitoring scheme, do you organise a meeting regarding monitoring methods or you are seeking for volunteer counters for the next breeding season? Please, let us know and tell us about your news!
September issue of the EBCC newsletter has been spread right now. The next issue will be out in the first half of December.
Did you miss some older issues? Check the EBCC e-mail newsletter archive!
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Name of scheme: Slovene monitoring of common farmland birds (Slovenski monitoring pogostih ptic kmetijske krajine)
Organisation: DOPPS-BirdLife Slovenia
Start: 2007 pilot year, 2008 start of regular monitoring
Number of fieldworkers: 30-40
Habitats recorded: yes
Methods: line transect with two belts (50 m and beyond)
Selection of plots: stratified non-random
Sustainable support: yes
Reference: Latest report 2017.
Contact: Primož Kmecl, DOPPS-BirdLife Slovenia, Trzaska cesta 2, SI-1000 Ljubljana, e-mail: email@example.com.
Indicators produced are used as official indicators in the country: yes
Name of scheme: Monitoring Häufige Brutvögel (Monitoring of common breeding birds)
Organisation: Swiss Ornithological Institute
Number of fieldworkers: 200
Habitats recorded: no
Methods: territory mapping
Selection of plots: systematic
Sustainable support: yes
Schmid, H., M. Kestenholz, P. Knaus, L. Rey & T. Sattler (2018): Zustand der Vogelwelt in der Schweiz: Sonderausgabe zum Brutvogelatlas 2013–2016. Schweizerische Vogelwarte, Sempach. Download PDF (4,5 MB)
Schmid, H., M. Kestenholz, P. Knaus, L. Rey & T. Sattler (2018): The State of Birds in Switzerland: Special Issue on the Breeding Bird Atlas 2013–2016. Swiss Ornithological Institute, Sempach. Download PDF (4,5 MB)
Schmid, H., M. Kestenholz, P. Knaus, L. Rey & T. Sattler (2018) : État de l’avifaune en Suisse : Édition spéciale liée à l’atlas des oiseaux nicheurs 2013-2016. Station ornithologique suisse, Sempach. Download PDF (4,5 MB)
Schmid, H., M. Kestenholz, P. Knaus, L. Rey & T. Sattler (2018): Situazione dell’avifauna in Svizzera: Edizione speciale per l’Atlante degli uccelli nidificanti 2013-2016. Stazione ornitologica svizzera, Sempach. Download PDF (4,5 MB)
Contact: Hans Schmid & Thomas Sattler, Swiss Ornithological Institute, Sempach, CH-6204, Switzerland, e-mail: firstname.lastname@example.org, email@example.com
Indicators produced are used as official indicators in the country: yes